(1) Field of the Invention
The present invention relates to a semiconductor integrated circuit which reduces the influence of noise from the digital circuit block, on the analog circuit block, both the circuit blocks being formed on the same semiconductor substrate.
(2) Description of the Related Art
FIG. 1 shows an example of a block diagram of a mobile phone. The signal received by an antenna 101 is amplified and demodulated in the receiving unit 200 through the antenna switch 102, and processed in the baseband processing unit 500 and the control processing unit 600. After that, the signal is outputted to the speaker unit 701 as sound, or to the display unit 702 as an image. On the other hand, the signal inputted through the input unit 703 is processed in the control processing unit 600 and the baseband processing unit 500, modulated and amplified in the sending unit 400, and is sent from the antenna 101 through the antenna switch 102. The local unit 300 generates a local signal and supplies it to the receiving unit 200 and the sending unit 400.
The receiving unit 200 includes a low noise amplifier 201 that amplifies receiving signals, a band limitation filter 202 that removes unnecessary waves of the output signal in the low noise amplifier 201, and a demodulator 203 that demodulates the output of the band limitation filter 202. On the other hand, the sending unit 400 includes a modulator 401 that performs modulation based on the output signal of the baseband processing unit 500, a band limitation filter 402 that removes unnecessary waves of the output signal of the modulator 401, and an electric amplifier 403 that amplifies the output signal of the band limitation filter 402. The local signal generated in the local unit 300 is supplied to the demodulator 203 and the modulator 401.
Recently, mobile apparatuses represented by mobile phones have been downsized, and display devices have been upsized and have been made more multifunctional. Accompanied by this, wireless parts are desired to be downsized. However, for example, in a block diagram of a conventional mobile phone shown in FIG. 1, the low noise amplifier 201, the demodulator 203, the modulator 401, the local unit 300 and the like are made into a semiconductor circuit independently. This is the cause of the problem that many numbers of components are needed and a bigger area for mounting such components is also needed.
In order to solve this problem, as shown in an example of a block diagram shown in FIG. 2, a semiconductor integrated circuit 100 into which the low noise amplifier 201, the demodulator 203, the modulator 401, and the local unit 300 are integrated has developed.
FIG. 3 shows an example of a layout diagram of a semiconductor integrated circuit 100 on the semiconductor substrate. In the synthesizer circuit 3 that is one of the circuits integrated on the semiconductor substrate 1 and that constitutes a part of the local unit 300, digital processing is performed resulting in generating noise. In order to reduce the influence of the noise generated by the synthesizer circuit 3 on the receiving properties of the low noise amplifier circuit 2 that is also one of the circuits integrated on the semiconductor substrate 1 and that constitutes the low noise amplifier 201, the low noise amplifier 2 and the synthesizer circuit 3 are formed in a way that the distance between the blocks of both circuits is sufficiently large.
Also, as shown in document 1: Japanese-Laid Open Patent application No. 2001-244416 publication (FIG. 4 and FIG. 5), a similar effect can be obtained by placing a circuit that is hardly affected by the circuit being a noise source between the low noise amplifier circuit 2 and the synthesizer circuit 3.